U.S. patent application number 14/910190 was filed with the patent office on 2016-06-23 for vehicle control device.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Wanleng ANG, Keisuke MORISAKI, Yoshitaka NIIMI, Masaki OKAMURA, Shintaro TSUJII, Hideaki YAGUCHI.
Application Number | 20160176295 14/910190 |
Document ID | / |
Family ID | 51429323 |
Filed Date | 2016-06-23 |
United States Patent
Application |
20160176295 |
Kind Code |
A1 |
NIIMI; Yoshitaka ; et
al. |
June 23, 2016 |
VEHICLE CONTROL DEVICE
Abstract
A vehicle control device that controls a vehicle including a
first electric motor that is driven at a rotation speed
synchronized with a rotation speed of a drive shaft of the vehicle
includes an electronic control unit. The electronic control unit is
configured to carry out first determination that determines whether
the rotation speed of the first electric motor is lower than or
equal to a first threshold and whether a stop operation that stops
the vehicle is being carried out, and to carry out second
determination that the vehicle is stopped when the electronic
control unit has determined in the first determination that the
rotation speed of the first electric motor is lower than or equal
to the first threshold and the stop operation is being carried
out.
Inventors: |
NIIMI; Yoshitaka; (Anjo-shi,
Aichi-ken, JP) ; OKAMURA; Masaki; (Miyoshi-shi,
Aichi-ken, JP) ; TSUJII; Shintaro; (Miyoshi-shi,
Aichi-ken, JP) ; ANG; Wanleng; (Okazaki-shi,
Aichi-ken, JP) ; YAGUCHI; Hideaki; (Okazaki-shi,
Aichi-ken, JP) ; MORISAKI; Keisuke; (JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi, Aichi-ken |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
51429323 |
Appl. No.: |
14/910190 |
Filed: |
August 5, 2014 |
PCT Filed: |
August 5, 2014 |
PCT NO: |
PCT/IB2014/001461 |
371 Date: |
February 4, 2016 |
Current U.S.
Class: |
701/22 |
Current CPC
Class: |
Y02T 10/7072 20130101;
Y02T 10/70 20130101; B60L 50/40 20190201; Y02T 10/62 20130101; B60L
2210/40 20130101; B60L 2240/12 20130101; B60L 50/16 20190201; B60L
3/12 20130101; B60L 15/007 20130101; Y02T 10/72 20130101; B60L
50/61 20190201; Y02T 10/64 20130101; B60L 2250/26 20130101; B60L
2240/80 20130101; B60L 15/20 20130101; B60L 2240/421 20130101; B60L
2240/423 20130101; B60L 3/0069 20130101; B60L 15/2009 20130101;
B60L 58/20 20190201 |
International
Class: |
B60L 3/12 20060101
B60L003/12; B60L 3/00 20060101 B60L003/00; B60L 15/20 20060101
B60L015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2013 |
JP |
2013-163384 |
Claims
1. A vehicle control device that controls a vehicle including a
first electric motor that is driven at a rotation speed
synchronized with a rotation speed of a drive shaft of the vehicle,
the vehicle control device comprising: an electronic control unit
configured to: (a) carry out first determination as to whether the
rotation speed of the first electric motor is lower than or equal
to a first threshold and whether a stop operation that stops the
vehicle is being carried out, and (b) carry out second
determination that the vehicle is stopped when in the first
determination the electronic control unit determines that the
rotation speed of the first electric motor is lower than or equal
to the first threshold and the stop operation is being carried
out.
2. The vehicle control device according to claim 1, wherein the
first electric motor is a three-phase alternating-current motor,
the vehicle includes a pair of serially connected first switching
element and second switching element in each of the three phases of
the first electric motor, the vehicle further includes a first
power converter that converts direct-current power to
alternating-current power, the direct-current power being supplied
to the first electric motor, and the electronic control unit is
configured to execute first control that controls the first power
converter such that a state of the first power converter is set to
a specific state where one of the set of first switching elements
all and the set of second switching elements all are in an off
state and at least one switching element of the other one of the
set of first switching elements and the set of second switching
elements is in an on state, when the electronic control unit has
carried out the second determination that the vehicle is
stopped.
3. The vehicle control device according to claim 2, wherein the
vehicle further includes a ground fault detector that detects a
ground fault in an electrical system including the first electric
motor, and the electronic control unit is configured to control the
first power converter such that the state of the first power
converter becomes the specific state when the electronic control
unit has carried out the second determination that the vehicle is
stopped, and the electronic control unit is configured to control
the ground fault detector such that the ground fault detector
carries out detection of the ground fault when the state of the
first power converter is the specific state.
4. The vehicle control device according to claim 3, wherein the
electronic control unit is configured to control the ground fault
detector such that the ground fault detector carries out detection
of the ground fault, and the electronic control unit is configured
to determine that the first electric motor is not stopped when a
stop cancellation condition is satisfied in the vehicle after the
detection is carried out.
5. The vehicle control device according to claim 4, wherein the
stop cancellation condition includes a condition that the rotation
speed of the first electric motor is higher than a second threshold
or a condition that the stop operation is not being carried
out.
6. The vehicle control device according to claim 4, wherein the
electronic control unit is configured to determine that the first
electric motor is not stopped when the stop cancellation condition
is satisfied, and the electronic control unit is configured to
cancel the specific state and end the detection of the ground fault
after determining that the first electric motor is not stopped.
7. The vehicle control device according to claim 1, wherein the
electronic control unit is configured to carry out the second
determination that the vehicle is stopped, when a duration of a
state is longer than or equal to a predetermined period, the state
being where in the first determination the electronic control unit
determines that the rotation speed of the first electric motor is
lower than or equal to the first threshold and the stop operation
is being carried out.
8. The vehicle control device according to claim 1, wherein the
vehicle further includes a second electric motor coupled to the
first electric motor via a power split mechanism, and the
electronic control unit is configured to further determine in the
first determination whether a rotation speed of the second electric
motor is lower than or equal to a third threshold, and the
electronic control unit is configured to carry out the second
determination that the vehicle is stopped when the electronic
control unit determines in the first determination that the
rotation speed of the first electric motor is lower than or equal
to the first threshold, the stop operation is being carried out and
the rotation speed of the second electric motor is lower than or
equal to the third threshold.
9. The vehicle control device according to claim 8, wherein the
second electric motor is a three-phase alternating-current motor,
the vehicle includes a pair of serially connected third switching
element and fourth switching element in each of the three phases of
the second electric motor, the vehicle further includes a second
power converter that converts direct-current power to
alternating-current power, the direct-current power being supplied
to the second electric motor, and the electronic control unit is
configured to execute second control that controls the second power
converter such that a state of the second power converter is set to
a specific state where one of the set of third switching elements
all and the set of fourth switching elements all are in an off
state and at least one switching element of the other one of the
set of third switching elements and the set of fourth switching
elements is in an on state, when the electronic control unit has
carried out the second determination that the vehicle is
stopped.
10. The vehicle control device according to claim 9, wherein the
vehicle further includes a ground fault detector that detects a
ground fault in an electrical system including the second electric
motor, and the electronic control unit is configured to execute the
second control that controls the second power converter such that
the state of the second power converter becomes the specific state
when the electronic control unit has determined that the second
electric motor is stopped, and the electronic control unit is
configured to control the ground fault detector such that the
ground fault detector carries out detection of the ground fault
when the state of the second power converter is the specific
state.
11. The vehicle control device according to claim 10, wherein the
electronic control unit is configured to control the ground fault
detector such that the ground fault detector carries out detection
of the ground fault, and the electronic control unit is configured
to determine that the second electric motor is not stopped when a
stop cancellation condition is satisfied in the vehicle after the
detection is carried out.
12. The vehicle control device according to claim 11, wherein the
stop cancellation condition includes a condition that the first
electric motor is not stopped or a condition that the rotation
speed of the second electric motor is higher than a fourth
threshold.
13. The vehicle control device according to claim 11, wherein the
stop cancellation condition includes a condition that the first
electric motor is not stopped or a condition that an engine is not
stopped.
14. The vehicle control device according to claim 11, wherein the
stop cancellation condition includes a condition that the rotation
speed of the first electric motor is higher than a second
threshold, a condition that the rotation speed of the second
electric motor is higher than a fourth threshold, or a condition
that the stop operation that stops the vehicle is not being carried
out.
15. The vehicle control device according to claim 11, wherein the
electronic control unit is configured to cancel the specific state
and end the detection of the ground fault of the second electric
motor when the stop cancellation condition is satisfied in the
vehicle.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to, for example, a technical field of
a vehicle control device that controls a vehicle including an
electric motor.
[0003] 2. Description of Related Art
[0004] In recent years, a vehicle including an electric motor (a
so-called motor) has become a focus of attention. As an example of
such a vehicle including an electric motor, there is known a hybrid
vehicle including both an electric motor and an internal combustion
engine (see, for example, Japanese Patent Application Publication
No. 2006-288051 (JP 2006-288051 A)). In addition, as such a vehicle
including an electric motor, there is known an electric vehicle
including an electric motor but not including an internal
combustion engine (see, for example, Japanese Patent Application
Publication No. 7-241002 (JP 7-241002 A)).
[0005] JP 2006-288051 A describes a technique for, in the thus
configured hybrid vehicle, executing three-phase short-circuit
control over the electric motor in order to early stop rotation of
the internal combustion engine when the rotation speed of the
internal combustion engine is lower than a predetermined rotation
speed.
[0006] JP 7-241002 A describes a technique for, in the thus
configured electric vehicle, setting all the switching elements in
one of two different types of switching elements to an off state
and setting at least one of the switching elements in the other one
of the two different types of switching elements to an on state in
order to carry out detection of a ground fault. The switching
elements constitute an inverter that supplies electric power to the
electric motor.
[0007] In the technique described in JP 7-241002 A, the states of
the switching elements are fixed at the time of carrying out an
operation to carry out detection of a ground fault, so it is
desirable that the electric motor be stopped. Thus, at the time of
carrying out an operation to carry out detection of a ground fault
by using the technique described in JP 7-241002 A, it is desirable
that the vehicle be stopped. That is, at the time of carrying out
an operation to carry out detection of a ground fault by using the
technique described in JP 7-241002 A, it is desirable to perform an
operation to determine whether the vehicle is stopped before an
operation to carry out detection of a ground fault is carried out.
In other words, after it is determined that the vehicle is stopped,
it is desirable to perform an operation to carry out detection of a
ground fault by using the technique described in JP 7-241002 A.
[0008] Therefore, as the operation to determine whether the vehicle
is stopped, it is conceivable that an operation to determine
whether the rotation speed of the internal combustion engine is
lower than a predetermined rotation speed (that is, the technique
described in JP 2006-288051 A) may be used. The "rotation speed of
the internal combustion engine" that is used as a determination
criterion as to whether the vehicle is stopped is typically
calculated on the basis of an output of a crank angle sensor.
However, considering the accuracy of the rotation speed of the
internal combustion engine, which is calculated from the output of
the crank angle sensor, there arises a technical problem that it is
difficult to highly accurately determine whether the vehicle is
stopped on the basis of the rotation speed of the internal
combustion engine. For example, there arises a technical problem
that it may be erroneously determined that the vehicle is stopped
because of, for example, an accuracy error of the rotation speed of
the internal combustion engine, which is calculated from the output
of the crank angle sensor, although the vehicle is not stopped.
[0009] The above-described technical problems will be described in
detail below. That is, the above-described technical problems can
arise not only when the operation to determine whether the vehicle
is stopped is carried out in association with the operation to
carry out detection of a ground fault by using the technique
described in JP 7-241002 A but also when the operation to determine
whether the vehicle is stopped is carried out.
SUMMARY OF THE INVENTION
[0010] A task that the invention is intended to solve includes the
above-described ones as examples. The invention provides a vehicle
control device that is able to highly accurately determine whether
the vehicle is stopped.
[0011] An aspect of the invention provides a vehicle control device
that controls a vehicle including a first electric motor that is
driven at a rotation speed synchronized with a rotation speed of a
drive shaft of the vehicle. The vehicle control device includes an
electronic control unit described as follows. That is, the
electronic control unit is configured to carry out first
determination as to whether the rotation speed of the first
electric motor is lower than or equal to a first threshold and
whether a stop operation that stops the vehicle is being carried
out, and configured to carry out second determination that the
vehicle is stopped when in the first determination the electronic
control unit determines that the rotation speed of the first
electric motor is lower than or equal to the first threshold and
the stop operation is being carried out.
[0012] With the thus configured vehicle control device, it is
possible to control the vehicle including the first electric motor.
The first electric motor is provided in the vehicle such that the
rotation speed of the first electric motor synchronizes with the
rotation speed of the drive shaft of the vehicle. The "state where
the rotation speed of the first electric motor synchronizes with
the rotation speed of the drive shaft" means a state where the
rotation speed of the first electric motor and the rotation speed
of the drive shaft have a correlation. Typically, the "state where
the rotation speed of the first electric motor synchronizes with
the rotation speed of the drive shaft" means a state where the
rotation speed of the first electric motor is directly proportional
to the rotation speed of the drive shaft (that is, (the rotation
speed of the first electric motor).times.K (where K is a selected
constant)=(the rotation speed of the drive shaft). The "state where
the rotation speed of the first electric motor synchronizes with
the rotation speed of the drive shaft" may be implemented by
directly coupling the rotary shaft of the first electric motor to
the drive shaft. Alternatively, the "state where the rotation speed
of the first electric motor synchronizes with the rotation speed of
the drive shaft" may be implemented by indirectly coupling the
rotary shaft of the first electric motor to the drive shaft via any
mechanical mechanism (for example, a speed reduction gear
mechanism).
[0013] In the thus configured vehicle control device, the
electronic control unit is configured to carry out the first
determination and the second determination in order to determine
whether the vehicle including the first electric motor is
stopped.
[0014] In the first determination, determination operation based on
the rotation speed of the first electric motor is performed.
Specifically, it is determined whether the rotation speed of the
first electric motor is lower than or equal to a first threshold.
In addition, in the first determination, determination operation
based on whether there is a stop operation that can stop the
vehicle is performed. Specifically, in the first determination, it
is determined whether the stop operation that stops the vehicle is
being carried out.
[0015] In the second determination, it is determined whether the
vehicle is stopped on the basis of the determination result of the
first determination. Specifically, in the second determination,
when it is determined in the first determination that the rotation
speed of the first electric motor is lower than or equal to the
first threshold and the stop operation is being carried out, it is
determined that the vehicle is stopped. On the other hand, in the
second determination, when it is determined in the first
determination that the rotation speed of the first electric motor
is not lower than or equal to the first threshold, it may be
determined that the vehicle is not stopped. Similarly, in the
second determination, when it is determined in the first
determination that the stop operation is not being carried out, it
may be determined that the vehicle is not stopped.
[0016] As described above, the vehicle control device according to
the invention is able to determine whether the vehicle is stopped
on the basis of not only the rotation speed of the first electric
motor but also whether there is the stop operation. Therefore, the
thus configured vehicle control device is able to relatively highly
accurately determine whether the vehicle is stopped in comparison
with a vehicle control device according to a first comparative
embodiment, which determines that the vehicle is stopped when a
rotation speed of an internal combustion engine, of which detection
accuracy can be lower than the detection accuracy of the rotation
speed of the first electric motor, is lower than or equal to a
predetermined threshold. In addition, the vehicle control device
according to the invention is able to relatively highly accurately
determine whether the vehicle is stopped in comparison with a
vehicle control device according to a second comparative
embodiment, which determines that the vehicle is stopped when the
rotation speed of the first electric motor is lower than or equal
to a predetermined threshold without determining whether the stop
operation is being carried out.
[0017] In the vehicle control device, the first electric motor may
be a three-phase alternating-current motor, the vehicle may include
a pair of serially connected first switching element and second
switching element in each of the three phases of the first electric
motor, the vehicle may further include a first power converter that
converts direct-current power to alternating-current power, the
direct-current power being supplied to the first electric motor.
The electronic control unit may be configured to execute first
control that controls the first power converter such that a state
of the first power converter is set to a specific state where one
of the set of first switching elements all and the set of second
switching elements all are in an off state and at least one
switching element of the other one of the set of first switching
elements and the set of second switching elements is in an on
state, when the electronic control unit has carried out the second
determination that the vehicle is stopped.
[0018] In the control device, the first electric motor, which is a
three-phase alternating-current motor, is driven with electric
power that is supplied from the first power converter (that is,
alternating-current power).
[0019] In order to supply electric power to the first electric
motor, which is a three-phase alternating-current motor, the first
power converter includes the pair of serially connected first
switching element (for example, the switching element electrically
connected between a high-voltage-side terminal of a power supply
and the first electric motor) and second switching element (for
example, a switching element electrically connected between a
low-voltage-side terminal of the power supply and the first
electric motor) in each of the three phases. That is, the first
power converter includes the first and second switching elements
arranged in the U phase, the first and second switching elements
arranged in the V phase and the first and second switching elements
arranged in the W phase.
[0020] Particularly, the electronic control unit includes first
control that controls the first power converter. In the first
control, the first power converter may be controlled such that the
state of the first power converter becomes the specific state
(typically, the state of the first power converter is fixed to the
specific state) when in the second determination the electronic
control unit determines that the vehicle is stopped. Here, the
"specific state" is a state where one of the set of first switching
elements and the set of second switching elements all are in an off
state (that is, an interrupted state) and at least one of the other
one of the set of first switching elements and the set of second
switching elements is in an on state (that is, a connected
state).
[0021] Here, when the state of the first power converter is the
specific state, there is a concern that electric power required to
cause the vehicle to travel is not supplied from the first power
converter to the first electric motor. In this aspect, in the first
control, it is possible to control the first power converter such
that the state of the first power converter becomes the specific
state (typically, the state of the first power converter is fixed
to the specific state) when in the second determination the
electronic control unit determines that the vehicle is stopped.
Particularly, because it is possible to highly accurately determine
in the second determination that the vehicle is stopped as
described above, the first control is able to control the first
power converter such that the state of the first power converter
becomes the specific state when the vehicle is exactly stopped.
That is, the first control is able to control the first power
converter such that the state of the first power converter becomes
the specific state at the timing at which there is no concern that
the state of the first power converter does not influence running
of the vehicle.
[0022] In the thus configured vehicle control device including the
first control, the vehicle may further include a ground fault
detector that detects a ground fault in an electrical system
including the first electric motor. The electronic control unit may
be configured to control the first power converter such that the
state of the first power converter becomes the specific state when
the electronic control unit has carried out the second
determination that the vehicle is stopped and configured to control
the ground fault detector such that the ground fault detector
carries out detection of the ground fault when the state of the
first power converter is the specific state.
[0023] In the thus configured vehicle control device, the ground
fault detector is able to detect a ground fault in part or all of
the electrical system including the first electric motor (for
example, the electrical system from the power supply to the first
electric motor via the power converter). The ground fault detector,
typically, may detect whether there is a ground fault by detecting
fluctuations in the state of the electrical system due to whether
there is a ground fault in the electrical system with any method.
For example, because of whether there is a ground fault in the
electrical system, the impedance in the electrical system can
fluctuate by the amount of the impedance of a ground fault path
that is formed as a result of a ground fault. Thus, the ground
fault detector may detect whether there is a ground fault by
detecting fluctuations in the impedance (or fluctuations in the
potential of the electrical system due to fluctuations in the
impedance) with any method.
[0024] The electronic control unit may be particularly configured
to control the ground fault detector such that the ground fault
detector carries out detection of a ground fault when the state of
the first power converter is the specific state in addition to
control over the first power converter in the first control.
[0025] When the ground fault detector is carrying out detection of
the ground fault, the state of the first power converter preferably
does not fluctuate (in other words, the state of the first power
converter is fixed). This is because there is a concern that the
ground fault detector erroneously detects fluctuations in the state
of the electrical system due to fluctuations in the state of the
first power converter as fluctuations in the state of the
electrical system due to a ground fault. In the first control, in
order to control the first power converter such that the state of
the first power converter does not fluctuate, it is preferable to
highly accurately determine in the second determination whether the
vehicle is stopped (for example, to reliably determine that the
vehicle is stopped when the vehicle is actually stopped). Thus,
because it is possible to highly accurately determine in the second
determination whether the vehicle is stopped as described above,
there is a relatively high possibility that the state of the first
power converter is fixed (typically, the state of the first power
converter is fixed to the specific state) while the ground fault
detector is carrying out detection of the ground fault. Thus, the
ground fault detector is able to suitably carry out detection of
the ground fault.
[0026] In the vehicle control device, the electronic control unit
may be configured to control the ground fault detector such that
the ground fault detector carries out detection of the ground
fault, and the electronic control unit may be configured to
determine that the first electric motor is not stopped when a stop
cancellation condition is satisfied in the vehicle after the
detection is carried out. The stop cancellation condition may
include a condition that the rotation speed of the first electric
motor is higher than a second threshold or a condition that the
stop operation is not being carried out.
[0027] In the vehicle control device, the electronic control unit
may be configured to determine that the first electric motor is not
stopped when the stop cancellation condition is satisfied. The
electronic control unit may be configured to cancel the specific
state and end the detection of the ground fault after determining
that the first electric motor is not stopped.
[0028] In the vehicle control device according to the invention,
the electronic control unit may be configured to carry out the
second determination that the vehicle is stopped when a duration of
a state is longer than or equal to a predetermined period, the
state being where in the first determination the electronic control
unit determines that the rotation speed of the first electric motor
is lower than or equal to the first threshold and the stop
operation is being carried out.
[0029] With the thus configured vehicle control device, it is
possible to determine whether the vehicle is stopped in the second
determination on the basis of the duration of the state where it is
determined in the first determination that the rotation speed of
the first electric motor is lower than or equal to the first
threshold and the stop operation is being carried out. That is, in
the second determination, when the duration is longer than or equal
to the predetermined period, it may be determined that the vehicle
is stopped. On the other hand, in the second determination, when
the duration is not longer than or equal to the predetermined
period, it may be determined that the vehicle is not stopped.
[0030] In the thus configured vehicle control device, by
determining whether the vehicle is stopped, it is possible to
further highly accurately determine in the second determination
whether the vehicle is stopped. Particularly, in the second
determination, it is possible to further highly accurately
determine whether the vehicle is stopped, for example, when hunting
is occurring in the rotation speed of the first electric motor (or
the rotation speed of the first electric motor is instable). In
terms of the point that it is possible to suppress frequent
fluctuations in the determination result as to whether the vehicle
is stopped because of the influence of hunting, or the like (in
addition, frequent fluctuations in the state of the first power
converter), the vehicle control device is able to implement
suitable detection of a ground fault with the use of the ground
fault detector as described above.
[0031] In the vehicle control device, the vehicle may further
include a second electric motor coupled to the first electric motor
via a power split mechanism. The electronic control unit may be
configured to further determine in the first determination whether
a rotation speed of the second electric motor is lower than or
equal to a third threshold, and configured to carry out the second
determination that the vehicle is stopped when the electronic
control unit determines in the first determination that the
rotation speed of the first electric motor is lower than or equal
to the first threshold, the stop operation is being carried out and
the rotation speed of the second electric motor is lower than or
equal to the third threshold.
[0032] With the thus configured control device, the vehicle may
include the plurality of electric motors. That is, the vehicle may
include the second electric motor coupled to the first electric
motor via the power split mechanism (for example, a planetary gear
mechanism, or the like) in addition to the first electric motor.
The rotation speed of the second electric motor does not need to be
synchronized with the rotation speed of the drive shaft.
[0033] When the vehicle includes the second electric motor in this
way, it may be further determined in the first determination
whether the rotation speed of the second electric motor is lower
than or equal to the third threshold. In the second determination,
it may be determined whether the vehicle is stopped further on the
basis of the determination result as to whether the rotation speed
of the second electric motor is lower than or equal to the third
threshold. As will be described in detail later with reference to
the drawings, in the second determination, it may be determined
whether the vehicle is stopped not on the basis of the
determination result as to whether the rotation speed of the second
electric motor is lower than or equal to the third threshold.
[0034] In this way, with the thus configured vehicle control
device, in the second determination, it is possible to highly
accurately determine whether the vehicle is stopped even when the
vehicle includes the plurality of electric motors.
[0035] In the thus configured control device that controls the
vehicle including the second electric motor, the second electric
motor may be a three-phase alternating-current motor, the vehicle
may include a pair of serially connected third switching element
and fourth switching element in each of the three phases of the
second electric motor, and the vehicle may further include a second
power converter that converts direct-current power to
alternating-current power, the direct-current power being supplied
to the second electric motor. The electronic control unit may be
configured to execute second control that controls the second power
converter such that a state of the second power converter is set to
a specific state where one of the set of third switching elements
all and the set of fourth switching elements all are in an off
state and at least one switching element of the other one of the
set of third switching elements and the set of fourth switching
elements is in an on state, when the electronic control unit has
carried out the second determination that the vehicle is
stopped.
[0036] With the thus configured vehicle control device, for a
similar reason to that of the above-described control device
including the first control, it is possible to control the second
power converter in the second control such that the state of the
second power converter becomes the specific state at the timing at
which there is no concern that the state of the second power
converter does not influence running of the vehicle.
[0037] In the vehicle control device, the vehicle may further
include a ground fault detector that detects a ground fault in an
electrical system including the second electric motor, and the
electronic control unit may be configured to execute the second
control that controls the second power converter such that the
state of the second power converter becomes the specific state when
the electronic control unit has determined that the second electric
motor is stopped, and configured to control the ground fault
detector such that the ground fault detector carries out detection
of the ground fault when the state of the second power converter is
the specific state.
[0038] In the vehicle control device, the electronic control unit
may be configured to control the ground fault detector such that
the ground fault detector carries out detection of the ground
fault, and the electronic control unit may be configured to
determine that the second electric motor is not stopped when a stop
cancellation condition is satisfied in the vehicle after the
detection is carried out. The stop cancellation condition may
include a condition that the first electric motor is not stopped or
a condition that the rotation speed of the second electric motor is
higher than a fourth threshold. The stop cancellation condition may
include a condition that the first electric motor is not stopped or
a condition that an engine is not stopped. The stop cancellation
condition may include a condition that the rotation speed of the
first electric motor is higher than the second threshold, a
condition that the rotation speed of the second electric motor is
higher than the fourth threshold, or a condition that the stop
operation that stops the vehicle is not being carried out.
[0039] In the vehicle control device, the electronic control unit
may be configured to cancel the specific state and end the
detection of the ground fault of the second electric motor when the
stop cancellation condition is satisfied in the vehicle.
[0040] The above-described operation and advantages of the vehicle
control device become apparent from embodiments that will be
described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Features, advantages, and technical and industrial
significance of exemplary embodiments of the invention will be
described below with reference to the accompanying drawings, in
which like numerals denote like elements, and wherein:
[0042] FIG. 1 is a block diagram that shows the configuration of a
vehicle according to a first embodiment;
[0043] FIG. 2 is a flowchart that shows the flow of a stop
determination operation according to the first embodiment;
[0044] FIG. 3 is a timing chart that shows a rotation speed of a
motor generator, a brake depression force, whether a stop
determination condition is satisfied and a stop determination
result of the vehicle according to the first embodiment;
[0045] FIG. 4 is a block diagram that shows the configuration of a
vehicle according to a second embodiment;
[0046] FIG. 5 is a flowchart that shows the flow of a first
operation example of a stop determination operation according to
the second embodiment;
[0047] FIG. 6 is a flowchart that shows the flow of a second
operation example of the stop determination operation according to
the second embodiment; and
[0048] FIG. 7 is a flowchart that shows the flow of a third
operation example of the stop determination operation according to
the second embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
[0049] Hereinafter, first and second embodiments of a vehicle
control device will be sequentially described.
[0050] Initially, the first embodiment will be described with
reference to FIG. 1 to FIG. 3. The configuration of a vehicle 1
according to the first embodiment will be described with reference
to FIG. 1. FIG. 1 is a block diagram that shows the configuration
of the vehicle 1 according to the first embodiment.
[0051] As shown in FIG. 1, the vehicle 1 includes a direct-current
power supply 11, a smoothing capacitor 12, an inverter 13, a motor
generator MG2, a rotation angle sensor 14, a drive shaft 15, a
drive wheel 16, an electronic control unit (ECU) 17, a brake sensor
18 and a ground fault detector 19. The inverter 13 is one specific
example of a "first power converter". The motor generator MG2 is
one specific example of a "first electric motor". The ECU 17 is one
specific example of a "control device for a vehicle".
[0052] The direct-current power supply 11 is a rechargeable
electrical storage device. The direct-current power supply 11 is,
for example, a secondary battery (such as a nickel-metal hydride
battery and a lithium ion battery) or a capacitor (such as an
electric double layer capacitor and a large-capacitance
capacitor).
[0053] The smoothing capacitor 12 is a voltage smoothing capacitor
connected between the positive electrode line of the direct-current
power supply 11 and the negative electrode line of the
direct-current power supply 11.
[0054] The inverter 13 converts direct-current power
(direct-current voltage), which is supplied from the direct-current
power supply 11, to alternating-current power (three-phase
alternating-current voltage). In order to convert direct-current
power (direct-current voltage) to alternating-current power
(three-phase alternating-current voltage), the inverter 13 includes
a U-phase arm, a V-phase arm and a W-phase arm. The U-phase arm
includes a positive-side switching element Q1 and a negative-side
switching element Q2. The V-phase arm includes a positive-side
switching element Q3 and a negative-side switching element Q4. The
W-phase arm includes a positive-side switching element Q5 and a
negative-side switching element Q6. The arms of the inverter 13 are
connected in parallel with one another between the positive
electrode line and the negative electrode line. The positive-side
switching element Q1 and the negative-side switching element Q2 are
connected in series with each other between the positive electrode
line and the negative electrode line. The same applies to the
positive-side switching element Q3 and the negative-side switching
element Q4, and the positive-side switching element Q5 and the
negative-side switching element Q6. A rectifier diode D1 is
connected to the positive-side switching element Q1. The rectifier
diode D1 flows current from the emitter terminal of the
positive-side switching element Q1 to the collector terminal of the
positive-side switching element Q1. Similarly, a rectifier diode D2
to a rectifier diode D6 are respectively connected to the
negative-side switching element Q2 to the negative-side switching
element Q6. A midpoint between the upper arm (that is, the
positive-side switching element) and lower arm (that is, the
negative-side switching element) of each of the three-phase arms in
the inverter 13 is connected to a corresponding one of three-phase
coils of the motor generator MG2. As a result, alternating-current
power (three-phase alternating-current voltage) that is generated
as a result of conversion operation of the inverter 13 is supplied
to the motor generator MG2.
[0055] The motor generator MG2 is a three-phase alternating-current
motor generator. The motor generator MG2 is driven so as to
generate torque required to cause the vehicle 1 to travel. The
torque generated by the motor generator MG2 is transmitted to the
drive wheel 16 via the drive shaft 15 mechanically coupled to the
rotary shaft of the motor generator MG2. The motor generator MG2
may regenerate (generate) electric power during braking of the
vehicle 1.
[0056] The rotation angle sensor 14 detects the rotation speed Ne2
of the motor generator MG2 (that is, the rotation speed of the
rotary shaft of the motor generator MG2). The rotation angle sensor
14 preferably directly detects the rotation speed Ne2 of the motor
generator MG2. An example of the rotation angle sensor 14 is, for
example, a resolver, such as a rotary encoder. The rotation angle
sensor 14 preferably outputs the detected rotation speed Ne2 to the
ECU 17.
[0057] The ECU 17 is an electronic control unit that controls the
operation of the vehicle 1. In the first embodiment, the ECU 17
includes an inverter control unit 171 and a stop determination unit
172 as physical, logical or functional processing blocks. The
inverter control unit 171 is one specific example of "first control
device". The stop determination unit 172 is one specific example of
"first determination device" and "second determination device".
[0058] The inverter control unit 171 is a processing block that
controls the operation of the inverter 13. The inverter control
unit 171 may control the operation of the inverter 13 by using a
known control method. For example, the inverter control unit 171
may control the operation of the inverter 13 by using a pulse width
modulation (PWM) control method.
[0059] The stop determination unit 172 executes stop determination
operation that determines whether the motor generator MG2 is
stopped. The stop determination operation will be described in
detail later (see FIG. 2 and FIG. 3), so the detailed description
is omitted here.
[0060] Considering the fact that the drive shaft 15 of the vehicle
1 is coupled to the rotary shaft of the motor generator MG2, the
rotation speed of the drive shaft 15 of the vehicle 1 synchronizes
with the rotation speed Ne2 of the rotary shaft of the motor
generator MG2. For example, the rotation speed of the drive shaft
15 of the vehicle 1 is directly proportional to the rotation speed
Ne2 of the rotary shaft of the motor generator MG2. Thus, when the
rotation speed Ne2 of the rotary shaft of the motor generator MG2
becomes zero as a result of a stop of the motor generator MG2, the
rotation speed of the drive shaft 15 should also become zero. A
state where the rotation speed of the drive shaft 15 is zero is
substantially equivalent to a state where the vehicle 1 is stopped.
Therefore, a stop of the motor generator MG2 substantially
corresponds to a stop of the vehicle 1. The stop determination unit
172 may determine whether the vehicle 1 is stopped in addition to
or instead of determination as to whether the motor generator MG2
is stopped.
[0061] The brake sensor 18 detects a brake depression force (that
is, a parameter indicating a force depressing a foot brake) BK. The
brake sensor 18 preferably outputs the detected brake depression
force BK to the ECU 17.
[0062] The ground fault detector 19 carries out detection of a
ground fault in an electrical system including the direct-current
power supply 11, the smoothing capacitor 12, the inverter 13 and
the motor generator MG2 (so-called motor driving system).
[0063] In order to carry out detection of a ground fault, the
ground fault detector 19 includes a coupling capacitor 191, an
oscillating circuit 192, a voltage detection circuit 193 and a
resistor 194.
[0064] A method in which the ground fault detector 19 carries out
detection of a ground fault is as follows. Initially, the
oscillating circuit 192 outputs a pulse signal (or
alternating-current signal) having a predetermined frequency. The
voltage detection circuit 193 detects the voltage at a node E,
which fluctuates because of the pulse signal. Here, if there occurs
a ground fault in the electrical system, a ground fault path from
the electrical system to a chassis ground (typically, the ground
fault path is equivalent to a circuit formed of a resistor or a
circuit in which a resistor and a capacitor are connected in
parallel with each other) is formed. As a result, the pulse signal
that is output from the oscillating circuit 192 is transmitted
through a path to the resistor 194, the coupling capacitor 191 and
the ground fault path. The voltage of the pulse signal at the node
E receives influence on the impedance of the ground fault path
(typically, the resistance value of the resistor included in the
equivalent circuit of the ground fault path). Thus, when the
voltage detection circuit 193 detects the voltage at the node E, it
is possible to carry out detection of a ground fault.
(1-2) Flow of Stop Determination Operation According to First
Embodiment
[0065] Subsequently, the flow of the stop determination operation
that is executed in the vehicle 1 according to the first embodiment
(that is, the stop determination operation that is executed by the
ECU 17) will be described with reference to FIG. 2. FIG. 2 is a
flowchart that shows the flow of the stop determination operation
according to the first embodiment.
[0066] As shown in FIG. 2, the stop determination unit 172
determines whether a predetermined stop determination condition is
satisfied (step S100).
[0067] The stop determination condition includes a stop
determination condition based on the rotation speed Ne2 of the
motor generator MG2. In FIG. 2, as an example of the stop
determination condition based on the rotation speed Ne2, the
condition that the absolute value of the rotation speed Ne2 of the
motor generator MG2 is lower than or equal to a predetermined
threshold N1 (that is, the relationship |Ne2|.ltoreq.N1 is
satisfied) is used.
[0068] As described above, a stop of the motor generator MG2
corresponds to a stop of the vehicle 1. Thus, the predetermined
threshold N1 for determining a stop of the motor generator MG2 may
be set to an appropriate value on the basis of the rotation speed
Ne2 of the motor generator MG2. The rotation speed Ne2 of the motor
generator MG2 is observed in a state where the vehicle 1 is
stopped. For example, where a "stop of the vehicle 1" means a state
where the speed of the vehicle 1 is zero or substantially zero, the
predetermined threshold N1 may be set to a value higher than or
equal to the rotation speed Ne2 of the motor generator MG2. Here,
the rotation speed Ne2 of the motor generator MG2 is observed in
the case where the speed of the vehicle 1 is zero.
[0069] In addition, the stop determination condition includes a
stop determination condition based on whether there is an operation
that can stop the vehicle 1 (hereinafter, referred to as "stop
operation" where appropriate). In FIG. 2, as an example of the stop
determination condition based on whether there is the stop
operation, the condition that the brake depression force BK is
larger than a predetermined threshold Pbks1 (that is, the
relationship BK>Pbks1 is satisfied) is used.
[0070] The stop operation is typically performed on the basis of a
driver's intention (that is, driver's voluntary operation).
However, the stop operation may be automatically performed
irrespective of a driver's intention (for example, automatically
under control of a controller, such as the ECU 17). A situation
that the stop operation is automatically performed can occur in,
for example, the vehicle 1 that executes automatic drive control
(that is, control for autonomously causing the vehicle 1 to travel
irrespective of whether there is a driver's operation).
[0071] The stop determination condition shown in FIG. 2 is only
illustrative. Thus, a stop determination condition different from
the stop determination condition shown in FIG. 2 may also be used.
For example, as long as it is possible to distinguish a state where
the vehicle 1 is stopped and a state where the vehicle 1 is not
stopped from each other on the basis of a difference in the
characteristics of the rotation speed Ne2, any condition that
utilizes a difference in the characteristics of the rotation speed
Ne2 may be used as the stop determination condition based on the
rotation speed Ne2. Similarly, as long as it is possible to
distinguish a state where the vehicle 1 is stopped and a state
where the vehicle 1 is not stopped from each other on the basis of
a difference in the characteristics of the stop operation, any
condition that utilizes a difference in the characteristics of the
stop operation may be used as the stop determination condition
based on whether there is the stop operation.
[0072] The stop determination condition based on whether there is
the stop operation is preferably a stop determination condition
based on whether there is an operation that is directly intended to
stop the vehicle 1. The operation that is directly intended to stop
the vehicle 1 is, for example, an operation that can apply braking
force to the vehicle 1 (for example, an action to operate a
selected brake, such as a foot brake and a side brake) and an
operation that is highly likely to be performed when the vehicle is
stopped (for example, an action to shift a shift lever to a P
range, or the like). Thus, for example, the condition that a
selected brake is operated may be used as the stop determination
condition based on whether there is the stop operation.
Alternatively, for example, the condition that a braking force due
to a selected brake is larger than a predetermined threshold (for
example, the condition that the above-described brake depression
force BK is larger than the predetermined threshold Pbks1) may be
used as the stop determination condition based on whether there is
the stop operation. Alternatively, for example, the condition that
the range of the shift lever is the P range may be used as the stop
determination condition based on whether there is the stop
operation.
[0073] However, the stop determination condition based on whether
there is the stop operation may be a stop determination condition
based on whether there is an operation that is not an operation
directly intended to stop the vehicle 1 but that can lead to a stop
of the vehicle 1 as a result. The operation that can lead to a stop
of the vehicle 1 is, for example, an operation that is highly
likely to be performed in advance of a stop of the vehicle (for
example, an operation to release the foot from the accelerator
pedal). Thus, for example, the condition that the accelerator pedal
is not operated may be used as the stop determination condition
based on whether there is the stop operation.
[0074] Alternatively, the stop determination condition based on
whether there is the stop operation may be a condition associated
with whether there is another operation that occurs because of the
stop operation. For example, another operation that occurs because
of the stop operation is, for example, an operation to set a torque
command value of creep to zero and an operation to set a torque
command value of the motor generator MG2 to zero. Thus, for
example, the condition that the torque command value of creep is
zero or the condition that the torque command value of the motor
generator MG2 is zero may be used as the stop determination
condition based on whether there is the stop operation.
[0075] When it is determined that the stop determination condition
is not satisfied as a result of determination of step S100 (No in
step S100), the stop determination unit 172 determines that the
motor generator MG2 is not stopped (step S109). Specifically, when
it is determined that the absolute value of the rotation speed Ne2
of the motor generator MG2 is not lower than the predetermined
threshold N1 (that is, |Ne2|>N1), the stop determination unit
172 determines that the motor generator MG2 is not stopped.
Similarly, when it is determined that the brake depression force BK
is not larger than the predetermined threshold Pbks1 (that is, BK
Pbks1), the stop determination unit 172 determines that the motor
generator MG2 is not stopped.
[0076] When it is determined that the motor generator MG2 is not
stopped, the ECU 17 ends the operation. However, the ECU 17 may
execute the operation from step S100 again.
[0077] On the other hand, when it is determined that the stop
determination condition is satisfied as a result of determination
of step S100 (Yes in step S100), the stop determination unit 172
starts a timer that measures a predetermined period (step
S101).
[0078] After the stop determination unit 172 starts the timer, the
stop determination unit 172 determines whether the state where the
stop determination condition is satisfied is continuing (step
S102).
[0079] When it is determined that the state where the stop
determination condition is satisfied is not continuing as a result
of determination of step S102 (No in step S102), the stop
determination unit 172 determines that the motor generator MG2 is
not stopped (step S109). That is, when it is determined that the
stop determination condition is not satisfied before the timer
ends, the stop determination unit 172 determines that the motor
generator MG2 is not stopped. In other words, when it is determined
that the duration of the state where the stop determination
condition is satisfied is not longer than or equal to a
predetermined period, the stop determination unit 172 determines
that the motor generator MG2 is not stopped.
[0080] On the other hand, when it is determined that the state
where the stop determination condition is satisfied is continuing
as a result of determination of step S102 (Yes in step S102), the
stop determination unit 172 executes the operation to determine
whether the state where the stop determination condition is
satisfied is continuing (step S102) repeatedly until the timer ends
(step S103).
[0081] After that, when the timer ends (Yes in step S103), the stop
determination unit 172 determines that the motor generator MG2 is
stopped (step S104). That is, when it is determined that the stop
determination condition has been satisfied in a period from the
start of the timer to the end of the timer, the stop determination
unit 172 determines that the motor generator MG2 is stopped. In
other words, when it is determined that the duration of the state
where the stop determination condition is satisfied is longer than
or equal to the predetermined period, the stop determination unit
172 determines that the motor generator MG2 is stopped.
[0082] Here, the operation to determine whether the motor generator
MG2 is stopped will be described by way of specific examples of the
rotation speed Ne2 and brake depression force BK with reference to
FIG. 3. FIG. 3 is a timing chart that shows the rotation speed Ne2,
the brake depression force BK, whether the stop determination
condition is satisfied and a stop determination result of the
vehicle 1.
[0083] As shown in FIG. 3, the brake depression force BK increases
as the foot brake starts being operated at time t0. With an
increase in the brake depression force BK, the rotation speed Ne2
also decreases.
[0084] When the vehicle 1 intends to stop because of the operation
of the foot brake, or the like, torsion tends to be generated in
the drive shaft 15 of the vehicle 1. As a result, with the torsion
of the drive shaft 15, hunting tends to occur in the rotation speed
of the drive shaft 15. Considering the fact that the rotary shaft
of the motor generator MG2 is coupled to the drive shaft 15,
hunting also tends to occur in the rotation speed Ne2 of the motor
generator MG2. FIG. 3 shows such hunting of the rotation speed Ne2
(in FIG. 3, upper limit fluctuations in the rotation speed Ne2,
which gradually converge).
[0085] After that, at time t1, the absolute value of the rotation
speed Ne2 becomes lower than or equal to the predetermined
threshold N1. However, at the timing of time t1, the brake
depression force BK is not larger than the predetermined threshold
Pbk1. Thus, the stop determination condition is not satisfied.
[0086] After that, at time t2, the brake depression force BK
becomes larger than the predetermined threshold Pbk1. Therefore, at
time t2, the stop determination condition is satisfied. However, at
the timing of time t2, the duration of the state where the stop
determination condition is satisfied is not longer than or equal to
the predetermined period, so the stop determination unit 172 does
not determine that the motor generator MG2 is stopped.
[0087] After that, due to the influence of hunting, at time t3 that
is the time before the predetermined period elapses from time t2
(that is, the time before the timer started at time t2 ends), the
absolute value of the rotation speed Ne2 exceeds the predetermined
threshold N1. That is, the stop determination condition is not
satisfied at time t3. As a result, the stop determination unit 172
does not determine that the motor generator MG2 is stopped.
[0088] After that, before time t4, the absolute value of the
rotation speed Ne2 becomes lower than or equal to the predetermined
threshold N1, but the duration of the state where the stop
determination condition is satisfied is not longer than or equal to
the predetermined period. Thus, in this case, the stop
determination unit 172 does not determine that the motor generator
MG2 is stopped.
[0089] After that, at time t4, the absolute value of the rotation
speed Ne2 becomes lower than or equal to the predetermined
threshold N1 again. Therefore, at time t4, the stop determination
condition is satisfied. However, at the timing of time t4, the
duration of the state where the stop determination condition is
satisfied is not longer than or equal to the predetermined period,
so the stop determination unit 172 does not determine that the
motor generator MG2 is stopped.
[0090] After that, at time t5 that is the time at which the
predetermined period has elapsed from time t4 (that is, the time at
which the timer started at time t2 ends), the stop determination
condition still continues being satisfied. Therefore, in the
example shown in FIG. 3, for the first time at the timing of time
t5, the stop determination unit 172 determines that the motor
generator MG2 is stopped.
[0091] Referring back to FIG. 2, when it is determined that the
motor generator MG2 is stopped, the ECU 17 (or the other
components, such as the ground fault detector 19) may execute an
operation that should be executed while the motor generator MG2 is
stopped. However, the ECU 17 (or the other components, such as the
ground fault detector 19) does not have to execute a special
operation even when it is determined that the motor generator MG2
is stopped.
[0092] In the first embodiment, when it is determined that the
motor generator MG2 is stopped, the inverter control unit 171
controls the operation of the inverter 13 so as to execute
three-phase short-circuit control (step S105). In the three-phase
short-circuit control, the state of the motor generator MG2 is
fixed in a three-phase short-circuit state. That is, the inverter
control unit 171 controls the operation of the inverter 13 such
that all the switching elements in one of the set of upper arms and
the set of lower arms are in an on state and all the switching
elements in the other one of the set of upper arms and the set of
lower arms are in an off state. For example, the inverter control
unit 171 may control the operation of the inverter 13 such that the
positive-side switching element Q1, the positive-side switching
element Q3 and the positive-side switching element Q5 are in an on
state and the negative-side switching element Q2, the negative-side
switching element Q4 and the negative-side switching element Q6 are
in an off state.
[0093] However, in step S105, the inverter control unit 171 may
control the operation of the inverter 13 so as to execute two-phase
short-circuit control. In the two-phase short-circuit control, the
state of the motor generator MG2 is fixed in a two-phase
short-circuit state. That is, the inverter control unit 171 may
control the operation of the inverter 13 such that any two
switching elements in one of the set of upper arms and the set of
lower arms are in an on state and the remaining one switching
element in the one of the set of upper arms and the set of lower
arms and all the switching elements in the other one of the set of
upper arms and the set of lower arms are in an off state.
[0094] Alternatively, in step S105, the inverter control unit 171
may control the operation of the inverter 13 so as to execute
control such that the state of the inverter 13 is fixed to a state
where only any one of the six switching elements included in the
inverter 13 is in an on state (while the remaining five switching
elements are in an off state).
[0095] In addition, in the first embodiment, when it is determined
that the motor generator MG2 is stopped, the ground fault detector
19 carries out detection of a ground fault in the electrical system
while the three-phase short-circuit control is being executed (step
S105). Because at least one of the six switching elements included
in the inverter 13 is in the on state, the ground fault detector 19
is able to detect not only a ground fault of a direct-current
portion (that is, a circuit portion on the direct-current power
supply 11 side of the inverter 13 in the electrical system) but
also a ground fault of an alternating-current portion (that is, a
circuit portion on the motor generator MG2 side of the inverter 13
in the electrical system).
[0096] In parallel with the operation of step S105, the stop
determination unit 172 determines whether a predetermined stop
cancellation condition is satisfied (step S106). In the first
embodiment, the stop cancellation condition, as well as the stop
determination condition, includes both a stop cancellation
condition based on the rotation speed Ne2 of the motor generator
MG2 and a stop cancellation condition based on whether there is the
stop operation. In FIG. 2, as an example of the stop cancellation
condition based on the rotation speed Ne2, a condition that the
absolute value of the rotation speed Ne2 of the motor generator MG2
is higher than a predetermined threshold N2 (that is, the
relationship |Ne2|>N2 is satisfied) is used. The predetermined
threshold N2 may be the same as the predetermined threshold N1 or
may be different from the predetermined threshold N1. Similarly, in
FIG. 2, as an example of the stop cancellation condition based on
whether there is the stop operation, the condition that the brake
depression force BK is smaller than a predetermined threshold Pbks2
(that is, the relationship BK<Pbks2 is satisfied) is used. The
predetermined threshold Pbks2 may be the same as the predetermined
threshold Pbks1 or may be different from the predetermined
threshold Pbks1.
[0097] The stop cancellation condition shown in FIG. 2 is only one
example. Thus, a stop cancellation condition different from the
stop cancellation condition shown in FIG. 2 may also be used. The
stop cancellation condition may be determined as needed in terms of
a similar viewpoint to that of the stop determination
condition.
[0098] The stop determination unit 172 may determine in step S106
whether the stop determination condition is satisfied in addition
to or instead of determination as to whether the stop cancellation
condition is satisfied. In this case, when it is determined that
the stop determination condition is not satisfied, the subsequent
operation may be executed in a similar mode to that in the case
where the stop cancellation condition is satisfied. On the other
hand, when it is determined that the stop determination condition
is satisfied, the subsequent operation may be executed in a similar
mode to that in the case where the stop cancellation condition is
not satisfied.
[0099] When it is determined that the stop cancellation condition
is not satisfied as a result of determination of step S106 (No in
step S106), the inverter control unit 171 continues to control the
operation of the inverter 13 so as to continue executing
three-phase short-circuit control. Similarly, the ground fault
detector 19 continues to carry out detection of a ground fault in
the electrical system.
[0100] On the other hand, when it is determined that the stop
cancellation condition is satisfied as a result of determination of
step S106 (Yes in step S106), the stop determination unit 172
determines that the motor generator MG2 is not stopped (step S107).
In this case, the inverter control unit 171 may control the
operation of the inverter 13 so as not to execute the three-phase
short-circuit control in which the state of the motor generator MG2
is fixed to the three-phase short-circuit state (step S108).
Similarly, the ground fault detector 19 ends detection of a ground
fault in the electrical system (step S108).
[0101] After that, the ECU 17 ends the operation. However, the ECU
17 may execute the operation from step S100 again.
[0102] As described above, in the first embodiment, the stop
determination unit 172 is able to determine whether the motor
generator MG2 (or the vehicle 1) is stopped on the basis of both
the stop determination condition based on the rotation speed Ne2 of
the motor generator MG2 and the stop determination condition based
on whether there is the stop operation. Where an existing stop
determination unit that determines whether the vehicle 1 is stopped
on the basis of only the stop determination condition based on the
rotation speed of the engine is regarded as a first comparative
embodiment, the stop determination unit 172 is able to more highly
accurately determine whether the motor generator MG2 (or the
vehicle 1) is stopped than the stop determination unit 172a
according to the first comparative embodiment. In addition, where
an existing stop determination unit that determines whether the
motor generator MG2 (or the vehicle 1) is stopped on the basis of
only the stop determination condition based on the rotation speed
Ne2 of the motor generator MG2 is regarded as a second comparative
embodiment, the stop determination unit 172 is able to more highly
accurately determine whether the motor generator MG2 (or the
vehicle 1) is stopped than the stop determination unit 172b
according to the second comparative embodiment. Hereinafter, the
reason will be described.
[0103] Initially, the first comparative embodiment will be
described in detail. The stop determination unit 172a according to
the first comparative embodiment, which determines that the vehicle
1 is stopped in the case where the rotation speed of the engine,
instead of the rotation speed Ne2 of the motor generator MG2, is
lower than or equal to a predetermined threshold, will be
described. The rotation speed of the engine is typically calculated
from the crank angle of the engine instead of being detected by a
detection mechanism that directly detects the rotation speed. The
crank angle of the engine is output from a crank angle sensor
installed in the engine. However, the accuracy of the rotation
speed of the engine, which is calculated from the crank angle, is
mostly lower than the accuracy of the rotation speed Ne2 of the
motor generator MG2, which is detected by the rotation angle sensor
14 (that is, the detection mechanism that directly detects the
rotation speed Ne2 of the motor generator MG2). Therefore, there is
a concern that the stop determination unit 172a according to the
first comparative embodiment erroneously determines that the
vehicle 1 is stopped because of the accuracy error, or the like, of
the rotation speed of the engine, which is calculated from the
crank angle, although the vehicle 1 is not stopped. Alternatively,
there is a concern that the stop determination unit 172a according
to the first comparative embodiment erroneously determines that the
vehicle 1 is not stopped although the vehicle 1 is stopped.
[0104] In contrast, the stop determination unit 172 according to
the first embodiment is able to determine whether the motor
generator MG2 (or the vehicle 1) is stopped on the basis of the
rotation speed Ne2 of the motor generator MG2, which is detected by
the rotation angle sensor 14. Considering that the accuracy of the
rotation speed Ne2 of the motor generator MG2, which is detected by
the rotation angle sensor 14, is mostly higher than the accuracy of
the rotation speed of the engine, which is calculated from the
crank angle, the stop determination unit 172 according to the first
embodiment is able to relatively highly accurately determine
whether the motor generator MG2 (or the vehicle 1) is stopped as
compared to the stop determination unit 172a according to the first
comparative embodiment.
[0105] Next, the second comparative embodiment will be described in
detail. The stop determination unit 172b according to the second
comparative embodiment, which determines that the motor generator
MG2 (or the vehicle 1) is stopped in the case where the rotation
speed Ne2 of the motor generator MG2 is lower than or equal to the
predetermined threshold N1 without determining whether there is the
stop operation, will be described. The stop determination unit 172b
according to the second comparative embodiment is also considered
to be able to relatively highly accurately determine whether the
vehicle 1 is stopped in comparison with the stop determination unit
172a according to the first comparative embodiment. However, the
rotation speed Ne2 of the motor generator MG2, which is detected by
the rotation angle sensor 14, can be instable (that is, can
fluctuate) upon reception of the influence of noise, or the like,
that occurs in the rotation angle sensor 14. For example, although
the actual rotation speed of the motor generator MG2 is zero, the
rotation speed Ne2 of the motor generator MG2, which is detected by
the rotation angle sensor 14, can be a numeric value other than
zero. Thus, there is a concern that, in some cases, the stop
determination unit 172b according to the second comparative
embodiment erroneously determines that the motor generator MG2 (or
the vehicle 1) is stopped although the motor generator MG2 (or the
vehicle 1) is not stopped. Alternatively, there is a concern that,
in some cases, the stop determination unit 172b according to the
second comparative embodiment erroneously determines that the motor
generator MG2 (or the vehicle 1) is not stopped although the motor
generator MG2 (or the vehicle 1) is stopped.
[0106] In contrast, the stop determination unit 172 is able to
determine whether the motor generator MG2 (or the vehicle 1) is
stopped on the basis of not only the rotation speed Ne2 of the
motor generator MG2 but also whether there is the stop operation.
When the stop operation is being carried out, there is a further
higher possibility that the motor generator MG2 (or the vehicle 1)
is stopped. Therefore, the stop determination unit 172 according to
the first embodiment is able to relatively highly accurately
determine whether the motor generator MG2 (or the vehicle 1) is
stopped as compared to the stop determination unit 172b according
to the second comparative embodiment.
[0107] In addition, the stop determination unit 172 is allowed to
determine that the motor generator MG2 (or the vehicle 1) is
stopped when it is determined that the duration of the state where
the stop determination condition is satisfied is longer than or
equal to the predetermined period. Thus, the stop determination
unit 172 is able to further highly accurately determine whether the
motor generator MG2 (or the vehicle 1) is stopped even when hunting
is occurring in the rotation speed Ne2 of the motor generator MG2
(or the rotation speed Ne2 of the motor generator MG2 is
instable).
[0108] Specifically, when hunting is occurring in the rotation
speed of the motor generator MG2, the state where the rotation
speed Ne2 is lower than or equal to the predetermined threshold N1
and the state where the rotation speed Ne2 is not lower than or
equal to the predetermined threshold N1 appear alternately in a
short period of time. If it is merely determined that the motor
generator MG2 (or the vehicle 1) is stopped in the case where the
rotation speed Ne2 is lower than or equal to the predetermined
threshold N1 in such a situation, there is a high possibility that
the determination result as to whether the motor generator MG2 (or
the vehicle 1) is stopped frequently fluctuates.
[0109] In contrast, in the first embodiment, the stop determination
unit 172 is allowed to determine that the motor generator MG2 (or
the vehicle 1) is not stopped in the case where it is determined
that the rotation speed Ne2 is lower than or equal to the
predetermined threshold N1 only in a short period of time because
of hunting, or the like. On the other hand, the stop determination
unit 172 is allowed to determine that the motor generator MG2 (or
the vehicle 1) is stopped when it is determined that the duration
of the rotation speed Ne2 is lower than or equal to the
predetermined threshold N1 is longer than or equal to a certain
time because of convergence of hunting, or the like. Thus, the stop
determination unit 172 is able to suitably determine whether the
motor generator MG2 (or the vehicle 1) is stopped while suppressing
frequent fluctuations in determination result as to whether the
motor generator MG2 (or the vehicle 1) is stopped because of the
influence of hunting, or the like.
[0110] In addition, the inverter control unit 171 according to the
first embodiment controls the inverter 13 so as to execute
three-phase short-circuit control while it is determined that the
motor generator MG2 (or the vehicle 1) is stopped. While the
three-phase short-circuit control is being executed, there is a
possibility that torque required to cause the vehicle 1 to travel
cannot be supplied from the inverter 13 to the motor generator MG2.
Thus, the inverter control unit 171 preferably controls the
inverter 13 so as to execute three-phase short-circuit control
while the motor generator MG2 (or the vehicle 1) is stopped.
Conversely, if the three-phase short-circuit control is executed
while the motor generator MG2 (or the vehicle 1) is not stopped,
there is a concern that the three-phase short-circuit control
influences running of the vehicle 1. Thus, the inverter control
unit 171 preferably controls the inverter 13 so as not to execute
three-phase short-circuit control while the motor generator MG2 (or
the vehicle 1) is not stopped. Thus, in the first embodiment, as
described above, the stop determination unit 172 is able to highly
accurately determine whether the motor generator MG2 (or the
vehicle 1) is stopped, so the inverter control unit 171 is able to
control the inverter 13 so as to execute three-phase short-circuit
control exactly while the motor generator MG2 (or the vehicle 1) is
stopped. That is, the inverter control unit 171 is able to control
the inverter 13 so as to execute three-phase short-circuit control
at the timing at which there is no concern that the three-phase
short-circuit control influences running of the vehicle 1.
[0111] In addition, the ground fault detector 19 according to the
first embodiment is able to carry out detection of a ground fault
while it is determined that the motor generator MG2 (or the vehicle
1) is stopped (in other words, while the inverter 13 is controlled
so as to execute three-phase short-circuit control). If the state
of the inverter 13 fluctuates while the ground fault detector 19 is
carrying out detection of a ground fault, there is a concern that
the state in the electrical system (for example, the impedance of a
path including the above-described ground fault path) fluctuates
because of fluctuations in the state of the inverter 13. As a
result, there is a concern that the ground fault detector 19
erroneously recognizes state fluctuations due to fluctuations in
the state of the inverter 13 (for example, the above-described
fluctuations in the voltage at the node E) as state fluctuations
due to a ground fault. Thus, in terms of improvement in the
accuracy of carrying out detection of a ground fault with the use
of the ground fault detector 19, the state of the inverter 13 is
preferably fixed to the three-phase short-circuit state (or another
state including the two-phase short-circuit state) while the ground
fault detector 19 is carrying out detection of a ground fault.
[0112] Here, when the accuracy of determination as to whether the
motor generator MG2 (or the vehicle 1) is stopped is relatively
low, there is a high possibility that the result of determination
as to whether the motor generator MG2 (or the vehicle 1) is stopped
frequently fluctuates because of the above-described noise,
hunting, or the like, as compared to the case where the
determination accuracy is relatively high. As a result, there is a
high possibility that the state of the inverter 13 frequently
fluctuates because of the fluctuations in the result of
determination as to whether the motor generator MG2 (or the vehicle
1) is stopped. As a result, there is a concern that the period in
which the state of the inverter 13 is fixed to the three-phase
short-circuit state becomes shorter than the period required to
carry out detection of a ground fault with the use of the ground
fault detector 19.
[0113] For such reasons, when it is highly accurately determined
whether the motor generator MG2 (or the vehicle 1) is stopped, the
state of the inverter 13 is easily fixed to the three-phase
short-circuit state. Thus, in the first embodiment, as described
above, the stop determination unit 172 is able to highly accurately
determine whether the motor generator MG2 (or the vehicle 1) is
stopped. Therefore, while the ground fault detector 19 is detecting
a ground fault, the state of the inverter 13 is relatively highly
likely to be fixed (typically, the state of the inverter 13 is
fixed to a specific state). Thus, the ground fault detector 19 is
able to suitably carry out detection of a ground fault.
[0114] In the above description, the vehicle 1 includes the single
motor generator MG2. Instead, the vehicle 1 may include a plurality
of the motor generators MG2. In this case, the vehicle 1 preferably
includes the inverter 13 and the rotation angle sensor 14 for each
motor generator MG2. In this case, the ECU 17 may execute the
above-described stop determination operation independently for each
motor generator MG2.
[0115] Next, a second embodiment will be described with reference
to FIG. 4 to FIG. 6. Like reference numerals and step numbers
denote similar components and operations to those of vehicle 1
according to the first embodiment, and the detailed description
thereof is omitted.
(2-1) Configuration of Vehicle According to Second Embodiment
[0116] Initially, the configuration of a vehicle 2 according to the
second embodiment will be described with reference to FIG. 4. FIG.
4 is a block diagram that shows the configuration of the vehicle 2
according to the second embodiment.
[0117] As shown in FIG. 4, the vehicle 2 according to the second
embodiment differs from the vehicle 1 according to the first
embodiment in that the vehicle 2 further includes an engine ENG, a
motor generator MG1, an inverter 13-1, a rotation angle sensor 14-1
and a power split mechanism 20. In addition, the vehicle 2
according to the second embodiment differs from the vehicle 1
according to the first embodiment in that the operation of the stop
determination unit 172 is different. The other components of the
vehicle 2 according to the second embodiment are the same as the
other components of the vehicle 1 according to the first
embodiment. However, for the sake of convenience of description, in
the second embodiment, the inverter 13 according to the first
embodiment is referred to as the inverter 13-2, and the rotation
angle sensor 14 according to the first embodiment is referred to as
the rotation angle sensor 14-2. For simplification of the drawings,
the detailed configuration of the ground fault detector 19 is
omitted; however, the ground fault detector 19 according to the
second embodiment is the same as the ground fault detector 19
according to the first embodiment.
[0118] The inverter 13-1 is connected in parallel with the inverter
13-2. The inverter 13-1 converts alternating-current power
(three-phase alternating-current voltage), generated through
regenerative power generation by the motor generator MG1, to
direct-current power (direct-current voltage). As a result, the
direct-current power supply 11 is charged with direct-current power
(direct-current voltage) generated as a result of conversion
operation by the inverter 13-1. Because the configuration of the
inverter 13-1 is the same as the configuration of the inverter
13-2, the detailed description of the configuration of the inverter
13-1 is omitted.
[0119] The motor generator MG1 is a three-phase alternating-current
motor generator. The motor generator MG1 regenerates electric power
(generates electric power) during braking of the vehicle 1. The
motor generator MG1 may be driven so as to generate torque required
to cause the vehicle 2 to travel.
[0120] The rotation angle sensor 14-1 detects the rotation speed
Ne1 of the motor generator MG1 (that is, the rotation speed of the
rotary shaft of the motor generator MG1). The rotation angle sensor
14-1 may be the same as the rotation angle sensor 14-2.
[0121] The engine ENG is an internal combustion engine, such as a
gasoline engine, and functions as a main power source of the
vehicle 2.
[0122] The power split mechanism 20 is a planetary gear mechanism
that includes a sun gear, a planetary carrier, pinion gears and a
ring gear (which are not shown). The power split mechanism 20
mainly splits the power of the engine ENG to two lines (that is, a
power line to be transmitted to the motor generator MG1 and a power
line to be transmitted to the drive shaft 15).
[0123] In the second embodiment, an example in which the vehicle 2
employs a so-called split (power split)-type hybrid system (for
example, Toyota hybrid system (THS)) will be described. Instead,
the vehicle 2 may employ a series or parallel hybrid system.
[0124] Subsequently, the flow of stop determination operation that
is executed by the vehicle 2 according to the second embodiment
(that is, the stop determination operation that is executed by the
ECU 17) will be described with reference to FIG. 5 to FIG. 7.
Hereinafter, first to third operation examples will be illustrated
as the stop determination operation that is executed in the vehicle
2 according to the second embodiment.
[0125] First, the flow of the first operation example of the stop
determination operation according to the second embodiment will be
described with reference to FIG. 5. FIG. 5 is a flowchart that
shows the flow of the first operation example of the stop
determination operation according to the second embodiment.
[0126] The first operation example is an operation to determine
whether the motor generator MG1 is stopped, and is an operation
that is executed in parallel with or before or after the
above-described stop determination operation according to the first
embodiment.
[0127] Specifically, as shown in FIG. 5, the stop determination
unit 172 determines whether a predetermined stop determination
condition is satisfied (step S210).
[0128] The stop determination condition of the first operation
example includes a stop determination condition based on the result
of the stop determination operation according to the first
embodiment (that is, the result of determination as to whether the
motor generator MG2 is stopped). In FIG. 5, as an example of the
stop determination condition based on the result of the stop
determination operation according to the first embodiment, the
condition that it is determined through the stop determination
operation according to the first embodiment that the motor
generator MG2 (or the vehicle 1) is stopped is used.
[0129] In addition, the stop determination condition of the first
operation example includes a stop determination condition based on
the rotation speed Ne1 of the motor generator MG1. In FIG. 5, as an
example of the stop determination condition based on the rotation
speed Ne1, the condition that the absolute value of the rotation
speed Ne1 of the motor generator MG1 is lower than or equal to a
predetermined threshold N3 (that is, the relationship
|Ne1|.ltoreq.N3 is satisfied) is used. The predetermined threshold
N3 may be the same as the predetermined value N1 according to the
first embodiment or may be different from the predetermined value
N1. The stop determination condition shown in FIG. 5 is only one
example, and may be modified as needed in terms of a similar
viewpoint to that of the first embodiment.
[0130] When it is determined that the stop determination condition
is not satisfied as a result of determination of step S210 (No in
step S210), the stop determination unit 172 determines that the
motor generator MG1 is not stopped (step S219).
[0131] On the other hand, when it is determined that the stop
determination condition is satisfied as a result of determination
of step S210 (Yes in step S210), the stop determination unit 172,
as in the case of the first embodiment, determines whether the
duration of the state where the stop determination condition is
satisfied is longer than or equal to the predetermined time (from
step S101 to step S103).
[0132] When it is determined that the duration of the state where
the stop determination condition is satisfied is not longer than or
equal to the predetermined time as a result of determination of
step S102 and step S103 (No in step S102), the stop determination
unit 172 determines that the motor generator MG1 is not stopped
(step S219).
[0133] On the other hand, when it is determined that the duration
of the state where the stop determination condition is satisfied is
longer than or equal to the predetermined time as a result of
determination of step S102 and step S103 (Yes in step S102 and Yes
in step S103), the stop determination unit 172 determines that the
motor generator MG1 is stopped (step S214). This is because, when
the rotation speed Ne1 of the motor generator MG1 is relatively low
(for example, several rpm to several tens of rpm) under a situation
that the motor generator MG2 is stopped, the rotation speed of the
engine ENG should also relatively decrease (for example, becomes
about several rpm) from an operation nomograph of the motor
generators MG1, MG2 and the engine ENG. However, considering that
it is almost impossible that the rotation speed of the engine ENG
becomes several rpm in accordance with the specifications of the
engine ENG, when the rotation speed Ne1 of the motor generator MG1
is relatively low under a situation that the motor generator MG2 is
stopped, the rotation speed of the engine ENG is estimated to be
substantially zero. That is, when the rotation speed Ne1 of the
motor generator MG1 is relatively low under a situation that the
motor generator MG2 is stopped, it is estimated that the engine ENG
is stopped. As a result, the motor generator MG1 is also estimated
to be substantially stopped from the operation nomograph.
[0134] After that, when it is determined that the motor generator
MG1 is stopped, the ECU 17 (or another component, such as the
ground fault detector 19) may execute the operation that should be
executed while the motor generator MG1 is stopped. In the first
operation example, when it is determined that the motor generator
MG1 is stopped, the inverter control unit 171 controls the
operation of the inverter 13-1 so as to execute three-phase
short-circuit control (step S215). In the three-phase short-circuit
control, the state of the motor generator MG1 is fixed in a
three-phase short-circuit state. However, in the first operation
example, as well as the first embodiment, the inverter control unit
171 may control the operation of the inverter 13-1 so as to execute
control in which the state of the motor generator MG1 is fixed to a
state other than the three-phase short-circuit state. In addition,
when it is determined that the motor generator MG1 is stopped, the
ground fault detector 19 carries out detection of a ground fault in
the electrical system while the three-phase short-circuit control
is being executed (step S215).
[0135] In the first operation example, the motor generator MG2 is
stopped, while there can occur a situation that it is determined
that the motor generator MG1 is not stopped. In this case, there is
a concern that the state of the inverter 13-1 is not fixed, so the
ground fault detector 19 does not need to carry out detection of a
ground fault in the electrical system.
[0136] In parallel with the operation of step S215, the stop
determination unit 172 determines whether the predetermined stop
cancellation condition is satisfied (step S216). In the first
operation example, the stop cancellation condition, as well as the
stop determination condition, includes both a stop cancellation
condition based on the result of stop determination operation
according to the first embodiment and a stop cancellation condition
based on the rotation speed Ne1 of the motor generator MG1. In FIG.
5, as an example of the stop cancellation condition based on the
result of the stop determination operation according to the first
embodiment, the condition that it is determined through the stop
determination operation according to the first embodiment that the
motor generator MG2 (or the vehicle 1) is not stopped is used. In
FIG. 5, as an example of the stop cancellation condition based on
the rotation speed Ne1, the condition that the absolute value of
the rotation speed Ne1 of the motor generator MG1 is higher than a
predetermined threshold N4 (that is, the relationship |Ne1|>N4
is satisfied) is used. The predetermined threshold N4 may be the
same as the predetermined threshold N2 according to the first
embodiment or may be different from the predetermined threshold N2.
The stop cancellation condition shown in FIG. 5 is only
illustrative, and may be modified as needed in terms of a similar
viewpoint to that of the first embodiment.
[0137] When it is determined that the stop cancellation condition
is not satisfied as a result of determination of step S216 (No in
step S216), the inverter control unit 171 continues to control the
operation of the inverter 13-1 so as to continue executing
three-phase short-circuit control. Similarly, the ground fault
detector 19 continues to carry out detection of a ground fault in
the electrical system.
[0138] On the other hand, when it is determined that the stop
cancellation condition is satisfied as a result of determination of
step S216 (Yes in step S216), the stop determination unit 172
determines that the motor generator MG1 is not stopped (step S217).
In this case, the inverter control unit 171 may control the
operation of the inverter 13-1 so as not to execute three-phase
short-circuit control in which the state of the motor generator MG1
is fixed to the three-phase short-circuit state (step S218).
Similarly, the ground fault detector 19 ends detection of a ground
fault in the electrical system (step S218).
[0139] As described above, according to the first operation example
of the second embodiment as well, similar advantageous effects to
the various advantageous effects obtained in the first embodiment
are suitably obtained. In addition, in the first operation example
of the second embodiment, the stop determination unit 172 is able
to highly accurately determine whether the vehicle 2 and each of
the motor generator MG1 and the motor generator MG2 are stopped
even when the vehicle 2 includes the plurality of motor generators
MG1, MG2.
[0140] Next, the flow of the second operation example of the stop
determination operation according to the second embodiment will be
described with reference to FIG. 6. FIG. 6 is a flowchart that
shows the flow of the second operation example of the stop
determination operation according to the second embodiment.
[0141] The second operation example, as well as the first operation
example, is also an operation to determine whether the motor
generator MG1 is stopped, and is an operation that is executed in
parallel with or before or after the above-described stop
determination operation according to the first embodiment.
[0142] Specifically, the second operation example differs from the
first operation example in that the stop determination condition
and the stop cancellation condition are different (step S220 and
step S226). The other operation of the second operation example may
be the same as the other operation of the first operation
example.
[0143] Specifically, the stop determination condition according to
the second operation example includes a stop determination
condition based on an operation situation of the engine ENG (for
example, a stop determination condition that the engine ENG is
stopped) instead of the stop determination condition based on the
rotation speed Ne1 of the first operation example. Similarly, the
stop cancellation condition according to the second operation
example includes a stop cancellation condition based on an
operation situation of the engine ENG (for example, a stop
cancellation condition that the engine ENG is not stopped) instead
of the stop cancellation condition based on the rotation speed Ne1
of the first operation example.
[0144] As described in the first operation example, when the engine
ENG is stopped under a situation that the motor generator MG2 is
stopped, it is estimated that the motor generator MG1 is also
substantially stopped. Thus, in the second operation example, the
stop determination unit 172 is able to suitably determine whether
the motor generator MG1 is stopped even when the stop determination
condition and the stop cancellation condition, based on the
operation situation of the engine ENG, are used. That is, in the
second operation example as well, similar advantageous effects to
the various advantageous effects obtained in the first operation
example, are suitably obtained.
[0145] The stop determination unit 172 may determine whether the
engine ENG is stopped on the basis of the rotation speed of the
engine ENG For example, the stop determination unit 172 may
determine that the engine ENG is stopped when the rotation speed of
the engine ENG is lower than or equal to a predetermined threshold.
Alternatively, the stop determination unit 172 may determine
whether the engine ENG is stopped on the basis of another parameter
or signal that defines the operation of the engine ENG.
[0146] Next, the flow of the third operation example of the stop
determination operation according to the second embodiment will be
described with reference to FIG. 7. FIG. 7 is a flowchart that
shows the flow of the third operation example of the stop
determination operation according to the second embodiment.
[0147] The above-described first operation example and second
operation example are operations to determine whether the motor
generator MG1 is stopped and operations that are executed in
parallel with or before or after the above-described stop
determination operation according to the first embodiment. On the
other hand, the third operation example is an operation to
collectively determine whether the motor generator MG1 and the
motor generator MG2 (or the vehicle 1) are stopped. Thus, the ECU
17 does not need to execute the above-described stop determination
operation according to the first embodiment when the third
operation example is executed.
[0148] Specifically, as shown in FIG. 7, the stop determination
unit 172 determines whether a predetermined stop determination
condition is satisfied (step S230). The stop determination
condition according to the third operation example includes the
stop determination condition according to the first embodiment
(that is, the stop determination condition based on the rotation
speed Ne2 of the motor generator MG2 and the stop determination
condition based on whether there is the stop operation). In
addition, the stop determination condition according to the third
operation example includes a stop determination condition based on
the rotation speed Ne1 of the motor generator MG1 (that is, part of
the stop determination condition according to the first operation
example). However, the stop determination condition according to
the third operation example may include the stop determination
condition based on the operation situation of the engine ENG (that
is, part of the stop determination condition according to the
second operation example) in addition to or instead of the stop
determination condition based on the rotation speed Ne1 of the
motor generator MG1 (that is, part of the stop determination
condition according to the first operation example).
[0149] When it is determined that the stop determination condition
is not satisfied as a result of determination of step S230 (No in
step S230), the stop determination unit 172 determines that at
least one of the motor generators MG1 and MG2 (or the vehicle 1) is
not stopped (step S239).
[0150] On the other hand, when it is determined that the stop
determination condition is satisfied as a result of determination
of step S230 (Yes in step S230), the stop determination unit 172,
as in the case of the first embodiment, determines whether the
duration of the state where the stop determination condition is
satisfied is longer than or equal to the predetermined time (step
S101 to step S103).
[0151] When it is determined that the duration of the state where
the stop determination condition is satisfied is not longer than or
equal to the predetermined time as a result of determination of
step S102 and step S103 (No in step S102), the stop determination
unit 172 determines that the motor generators MG1, MG2 (or the
vehicle 1) are not stopped (step S239).
[0152] On the other hand, when it is determined that the duration
of the state where the stop determination condition is satisfied is
longer than or equal to the predetermined time as a result of
determination of step S102 and step S103 (Yes in step S102 and Yes
in step S103), the stop determination unit 172 determines that the
motor generators MG1, MG2 (or the vehicle 1) are stopped (step
S234).
[0153] After that, when it is determined that the motor generators
MG1, MG2 (or the vehicle 1) are stopped, the ECU 17 (or another
component, such as the ground fault detector 19) may execute the
operation that should be executed while the motor generators MG1,
MG2 (or the vehicle 1) are stopped. In the third operation example,
when it is determined that the motor generators MG1, MG2 (or the
vehicle 1) are stopped, the inverter control unit 171 controls the
operations of the inverters 13-1, 13-2 so as to execute three-phase
short-circuit control (step S235). In the three-phase short-circuit
control, the state of each of the motor generators MG1, MG2 is
fixed in a three-phase short-circuit state. However, in the third
operation example, as well as the first embodiment, the inverter
control unit 171 may control the operations of the inverters 13-1,
13-2 so as to execute control in which the state of each of the
motor generators MG1, MG2 is set to a state other than the
three-phase short-circuit state. In addition, when it is determined
that the motor generators MG1, MG2 (or the vehicle 1) are stopped,
the ground fault detector 19 carries out detection of a ground
fault in the electrical system while the three-phase short-circuit
control is being executed (step S235).
[0154] In parallel with the operation of step S235, the stop
determination unit 172 determines whether a predetermined stop
cancellation condition is satisfied (step S236). The stop
cancellation condition according to the third operation example
includes the stop cancellation condition according to the first
embodiment (that is, the stop cancellation condition based on the
rotation speed Ne2 of the motor generator MG2 and the stop
cancellation condition based on whether there is the stop
operation). In addition, the stop cancellation condition according
to the third operation example includes the stop determination
condition based on the rotation speed Ne1 of the motor generator
MG1 (that is, part of the stop cancellation condition according to
the first operation example). However, the stop cancellation
condition according to the third operation example may include the
stop determination condition based on the operation situation of
the engine ENG (that is, part of the stop cancellation condition
according to the second operation example) in addition to or
instead of the stop determination condition based on the rotation
speed Ne1 of the motor generator MG1 (that is, part of the stop
cancellation condition according to the first operation
example).
[0155] When it is determined that the stop cancellation condition
is not satisfied as a result of determination of step S236 (No in
step S236), the inverter control unit 171 continues to control the
operations of the inverters 13-1, 13-2 so as to continue executing
three-phase short-circuit control. Similarly, the ground fault
detector 19 continues to carry out detection of a ground fault of
the electrical system.
[0156] On the other hand, when it is determined that the stop
cancellation condition is satisfied as a result of determination of
step S236 (Yes in step S236), the stop determination unit 172
determines that the motor generators MG1, MG2 (or the vehicle 1)
are not stopped (step S237). In this case, the inverter control
unit 171 may control the operations of the inverters 13-1, 13-2 so
as not to execute three-phase short-circuit control in which the
state of each of the motor generators MG1, MG2 is fixed to the
three-phase short-circuit state (step S238). Similarly, the ground
fault detector 19 ends detection of a ground fault in the
electrical system (step S238).
[0157] As described above, in the third operation example as well,
similar advantageous effects to the various advantageous effects
obtained in the first operation example are suitably obtained.
[0158] The invention is not limited to the above-described
embodiments; it may be modified as needed within the scope of the
invention read from the appended claims and the specification or
without departing from the spirit of the invention. A vehicle
control device having such modifications is also included in the
technical scope of the invention.
* * * * *